3D holographic display device and operating method of the same

ABSTRACT

A three-dimensional holographic display device includes a light emitting diode (LED) array including a plurality of light sources controlled to sequentially output light according to a preset pattern, a lens configured to refract light incident from the LED array, a spatial light modulator (SLM) configured to modulate light incident from the lens, and a processor configured to generate a plurality of holographic signals each comprising depth information adjusted according to an arrangement location of each of the plurality of light sources, and for each of the plurality of light sources, control the SLM to modulate the light based on a holographic signal corresponding to the light source.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based on and claims priority under 35 U.S.C. § 119to Korean Patent Application No. 10-2021-0024232, filed on Feb. 23,2021, in the Korean Intellectual Property Office, the disclosure ofwhich is incorporated by reference herein in its entirety.

BACKGROUND 1. Field

The disclosure relates to a three-dimensional holographic display deviceand an operating method of the same.

2. Description of Related Art

Three-dimensional holographic display devices may implement a highquality hologram in real time by using a spatial light modulator (SLM)capable of simultaneously controlling the amplitude and phase of light.As a three-dimensional holographic display device does not utilizebinocular parallax unlike a stereoscopic display, the three-dimensionalholographic display device may implement a real three-dimensional imagethat does not visually fatigue a user.

SUMMARY

Provided are a three-dimensional holographic display device and anoperating method of the same. The technical objectives to be achieved bythe disclosure are not limited to the above-described objectives, andother technical objectives may be inferred from the following exampleembodiments.

Additional aspects will be set forth in part in the description whichfollows and, in part, will be apparent from the description, or may belearned by practice of the example embodiments of the disclosure.

In accordance with an aspect of the disclosure, a three-dimensionalholographic display device includes a light emitting diode (LED) arrayincluding a plurality of light sources controlled to sequentially outputlight according to a preset pattern; a lens configured to refract lightincident from the LED array; a spatial light modulator (SLM) configuredto modulate light incident from the lens; and a processor configured togenerate a plurality of holographic signals each including depthinformation adjusted according to an arrangement location of each of theplurality of light sources; and for each of the plurality of lightsources, control the SLM to modulate the light based on a holographicsignal corresponding to the light source.

When a second light source of the plurality of light sources outputslight after a first light source of the plurality of light sourcesoutputs light according to the preset pattern, the processor may changea holographic image pattern displayed by the SLM at a timing when thesecond light source starts outputting the light, and the changedholographic image pattern may be formed by a second holographic signalof the plurality of holographic signals, the second holographic signalincluding second depth information adjusted according to an arrangementlocation of the second light source.

The LED array may change a light source that outputs light, at a cycleof at least 1 MHz.

The three-dimensional holographic display device may further include afilter configured to remove a noise component of the light modulated bythe SLM.

The processor may be further configured to drive the LED array in unitsof light source sets, each light source set including at least two lightsources of the plurality of light sources.

For each of the light source sets, a distance between the at least twolight sources in the light source set may be set such that holographicimages displayed in a space respectively by the at least two lightsources do not overlap each other.

For each of the light source sets, the processor may be furtherconfigured to adjust a brightness of at least some light sources amongthe at least two light sources in the light source set to be differentfrom a brightness of other light sources in the light source set.

The processor may be further configured to, when it is determined thatthe at least two light sources in a light source set of the light sourcesets comprise a defective light source, adjust a brightness of lightsources around the defective light source to compensate for a defect.

The LED array may include a first area including light sources of theplurality of light sources for displaying a first holographic imageperceived by a left eye of a user and a second area including lightsources of the plurality of light sources for displaying a secondholographic image perceived by a right eye of the user.

The three-dimensional holographic display device may further include adriving device configured to move the LED array in at least one of afirst direction, a second direction perpendicular to the firstdirection, and a third direction perpendicular to both of the firstdirection and the second direction, or rotate the LED array around atleast one of the first direction, the second direction, and the thirddirection, as an axis.

In accordance with an aspect of the disclosure, a method of operating athree-dimensional holographic display device includes generating aplurality of holographic signals each including depth informationadjusted according to an arrangement location of each of a plurality oflight sources in a light emitting diode (LED) array; controlling theplurality of light sources to sequentially output light according to apreset pattern; and for each of the plurality of light sources,controlling a spatial light modulator (SLM) to modulate light incidentfrom the LED array based on a holographic signal corresponding to thelight source.

The method may further include, when a second light source of theplurality of light sources outputs light after a first light source ofthe plurality of light sources outputs light according to the presetpattern, changing a holographic image pattern displayed by the SLM at atiming when the second light source starts outputting the light, whereinthe changed holographic image pattern is formed by a second holographicsignal of the plurality of holographic signals, the second holographicsignal including second depth information adjusted according to anarrangement location of the second light source.

The controlling of the plurality of light sources may include changing alight source that outputs light at a cycle of at least 1 MHz.

The method may further include removing a noise component of the lightmodulated by the SLM.

In the controlling of the plurality of light sources, the LED array maybe driven in units of light source sets, each light source set includingat least two light sources of the plurality of light sources.

For each of the light source sets, a distance between the at least twolight sources in the light source set may be set such that holographicimages displayed in a space respectively by the at least two lightsources do not overlap each other.

The method may further include, for each of the light source sets,adjusting a brightness of at least some light sources among the at leasttwo light sources in the light source set to be different from abrightness of other light sources in the light source set.

The method may further include, when it is determined that the at leasttwo light sources in a light source set of the light source sets includea defective light source, adjusting a brightness of light sources aroundthe defective light source to compensate for a defect.

The method may further include moving the LED array in at least one of afirst direction, a second direction perpendicular to the firstdirection, and a third direction perpendicular to both of the firstdirection and the second direction, or rotating the LED array around atleast one of the first direction, the second direction, and the thirddirection, as an axis.

A non-transitory computer-readable recording medium may have recordedthereon a program for executing the method of an above-noted aspect ofthe disclosure.

In accordance with an aspect of the disclosure, a holographic displaydevice includes a plurality of light sources configured to be operatedindependently of each other; a spatial light modulator (SLM) thatreceives light emitted by the plurality of light sources; and aprocessor configured to turn on and off the plurality of light sourcesin a repeating sequence; and sequentially provide a plurality of signalsto the SLM, each of the plurality of signals corresponding to adifferent step in the repeating sequence.

The holographic display device may be configured to form a holographicimage at a plurality of viewing windows, each of the plurality ofviewing windows corresponding to a different step in the repeatingsequence.

A location of each of the plurality of viewing windows may correspond toa location of one or more light sources, of the plurality of lightsources, that is turned on during the corresponding step in therepeating sequence.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features, and advantages of exampleembodiments of the disclosure will be more apparent from the followingdescription taken in conjunction with the accompanying drawings, inwhich:

FIG. 1 is a view of a configuration of a three-dimensional holographicdisplay device according to an embodiment;

FIG. 2 is a view of a viewing window formed by the three-dimensionalholographic display device of FIG. 1 ;

FIG. 3 is a view of an operation of a three-dimensional holographicdisplay device according to an embodiment;

FIG. 4 is a view of a configuration of a three-dimensional holographicdisplay device according to an embodiment;

FIG. 5 is a view of a process of implementing a multi-eye box by athree-dimensional holographic display device according to an embodiment;

FIG. 6 is a view of a process of extending an eye box by athree-dimensional holographic display device according to an embodiment;

FIG. 7 is a view of a configuration of an LED array according to anembodiment; and

FIG. 8 is a flowchart of a method of operating a three-dimensionalholographic display device, according to an embodiment.

DETAILED DESCRIPTION

Reference will now be made in detail to embodiments, examples of whichare illustrated in the accompanying drawings, wherein like referencenumerals refer to like elements throughout. In this regard, embodimentsmay have different forms and should not be construed as being limited tothe descriptions set forth herein. Accordingly, the embodiments aremerely described below, by referring to the figures, to explain aspects.As used herein, the term “and/or” includes any and all combinations ofone or more of the associated listed items. Expressions such as “atleast one of,” when preceding a list of elements, modify the entire listof elements and do not modify the individual elements of the list.

The terms used in the disclosure have been selected from currentlywidely used general terms in consideration of the functions in thedisclosure. However, the terms may vary according to the intention ofone of ordinary skill in the art, case precedents, and the advent of newtechnologies. Also, for special cases, meanings of the terms selected bythe applicant are described in detail in the description section.Accordingly, the terms used in the disclosure are defined based on theirmeanings in relation to the contents discussed throughout thespecification, not by their simple meanings.

In the specification, when a constituent element “connects” or is“connected” to another constituent element, the constituent elementcontacts or is connected to the other constituent element not onlydirectly, but also electrically through at least one of otherconstituent elements interposed therebetween. The expression ofsingularity in the specification includes the expression of pluralityunless clearly specified otherwise in context. Also, when a part may“include” a certain constituent element, unless specified otherwise, itmay not be construed to exclude another constituent element but may beconstrued to further include other constituent elements.

Terms such as “include” or “comprise” may not be construed tonecessarily include any and all constituent elements or steps describedin the specification, but may be construed to exclude some of theconstituent elements or steps or further include additional constituentelements or steps.

While such terms as “first,” “second,” etc., may be used to describevarious components, such components must not be limited to the aboveterms. The above terms are used only to distinguish one component fromanother.

The description of the following embodiments should not be construed aslimiting the scope of rights, and contents that can be easily inferredby those skilled in the art should be construed as belonging to thescope of the present specification. Hereinafter, example embodimentswill be described in detail with reference to the accompanying drawings.

FIG. 1 is a view of a configuration of a three-dimensional holographicdisplay device 10 according to an embodiment.

The three-dimensional holographic display device 10 may correspond toany electronic device capable of displaying a three-dimensionalholographic image. For example, the three-dimensional holographicdisplay device 10 may be applied to various electronic devices such asmonitors, TVs, mobile display devices, and the like.

Referring to FIG. 1 , the three-dimensional holographic display device10 may include a light-emitting diode (LED) array 110, a lens 120, aspatial light modulator (SLM) 130, and a processor 140. However, onlyconstituent elements related to embodiments are illustrated in thethree-dimensional holographic display device 10 of FIG. 1 . Accordingly,it is obvious to a person skilled in the art that general purposeconstituent elements other than the constituent elements of FIG. 1 maybe further included in the three-dimensional holographic display device10. For example, the three-dimensional holographic display device 10 mayfurther include a memory.

The memory is hardware for storing various pieces of data processed bythe three-dimensional holographic display device 10. For example, thememory may store pieces of data processed or to be processed by thethree-dimensional holographic display device 10. Furthermore, the memorymay include applications, drivers, and the like to be driven by thethree-dimensional holographic display device 10. In an example, thememory may store holographic signals generated by the processor 140.

The memory may include random access memory (RAM) such as dynamic randomaccess memory (DRAM), static random access memory (SRAM), and the like,read-only memory (ROM), electrically erasable programmable ROM (EEPROM),a CD-ROM, a Blu-ray disk, or other optical disc storages, a hard diskdrive (HDD), a solid state drive (SSD), or a flash memory, andfurthermore, other external storage devices accessible by thethree-dimensional holographic display device 10.

The LED array 110 may include a plurality of light sources that areindividually controllable (e.g., may be operated independently of eachother). For example, the LED array 110 may include a plurality of unitLEDs arranged in a two-dimensional array in row and column directions.Although FIG. 1 illustrates, as an embodiment, an example in which thethree-dimensional holographic display device 10 includes the LED array110, the LED array 110 may be replaced with a light source arrayincluding different types of light sources. For example, the LED array110 may be replaced with an array of various light sources of a laser, alaser diode (LD), and the like.

The lens 120 may include one or more lenses for refracting incidentlight from the LED array 110 in a certain direction. For example, thelens 120 may include at least one of a collimating lens for collimatingthe incident light from the LED array 110 into parallel light and afocusing lens for focusing light on a specific point. For example, thelens 120 may include only a focusing lens, or both a collimating lensand a focusing lens. The collimating lens may include a cylindrical lensor cylindrical lens array, and the focusing lens may be manufactured asa diffractive optical element in which the phase of a lens is recordedon a plane, or a holographic optical element. However, the disclosure isnot limited thereto.

Although FIG. 1 illustrates that the lens 120 is arranged in front ofthe SLM 130, the disclosure is not limited thereto. The lens 120 may bearranged at the rear of the SLM 130. Furthermore, when the lens 120includes a plurality of lenses, some lenses may be arranged in front ofthe SLM 130, and the other lenses may be arranged at the rear of the SLM130.

The SLM 130 may be a device capable of spatially converting light. TheSLM 130 may be of a transmission type or a reflection type. In anexample, the SLM 130 may include a liquid crystal on silicon (LCos)device or a liquid crystal display (LCD) device, but the disclosure isnot limited thereto. The SLM 130 may control at least one of strength(amplitude), color, or phase of light exiting the SLM 130, and mayinclude a matrix of a plurality of pixels that are individuallycontrollable.

The processor 140 may perform an overall function of controlling thethree-dimensional holographic display device 10. For example, theprocessor 140 may control operations of the LED array 110, the lens 120,and the SLM 130. The processor 140 may be implemented by an array of aplurality of logic gates, or a combination of a general purposemicroprocessor and a memory storing a program that is executable by themicroprocessor. Although FIG. 1 illustrates an example in which theprocessor 140 is provided separately from the SLM 130, the processor 140may be included in the SLM 130.

The processor 140 may generate a holographic signal. The holographicsignal may include a computer-generated hologram (CGH). To generate aCGH, a calculation method using a ray tracing method, a calculationmethod using a look-up table, a method using a fast Fourier transform,or the like may be used.

A holographic image pattern corresponding to the holographic signalgenerated by the processor 140 may be output by a plurality of pixels ofthe SLM 130, and an interference pattern of light rays may be generatedin a space due to diffraction of light passing through a plurality ofpixels of the SLM 130. A user may observe a three-dimensionalholographic image from an interference pattern propagated to each of aleft eye LP and a right eye RP. A process in which a user observes athree-dimensional holographic image is described below in detail withreference to FIG. 2 .

FIG. 2 is a view of a viewing window VW formed by the three-dimensionalholographic display device 10 of FIG. 1 .

Referring to FIG. 2 , when a light source 110 a included in the LEDarray 110 outputs light, a process in which a user U observes athree-dimensional holographic image is illustrated.

Light output from the light source 110 a included in the LED array 110may be refracted in a direction by passing through the lens 120. In anexample of FIG. 2 , as the lens 120 is a focusing lens, the lightpassing through the lens 120 may be focused toward a specific point inthe space. The SLM 130 may reconfigure a holographic image in the spaceby modulating the amplitude and/or phase of light input through the lens120.

However, a holographic image may be observed by the user U only in afield of vision due to a condition such as the characteristics of thelens 120, the pixel size of the SLM 130, and the like. As such, to thepupil of the user U, a field of vision for observing a holographic imagemay be referred to as a viewing window VW.

When the location of the pupil of the user U is out of the viewingwindow VW, a holographic image is not perceived by the user U and thusthere is a movement restriction for the user U to continuously observethe holographic image. According to the related art, a method ofcontinuously tracking the location of the pupil of the user U by using aseparate sensor, and performing movement of the location of the viewingwindow VW to fit to the tracked location of the pupil has been proposed.However, as the size of the viewing window VW is similar to the size ofthe pupil, which is merely about 3 mm to 8 mm, according to the relatedart, for accurate matching, a sensor having high precision, a processorcapable of performing a fast calculation, and the like are necessary.

The three-dimensional holographic display device according to thedisclosure proposes a technology that reduces a restriction in themovement of the user U even when the location of the pupil of the user Uis not continuously tracked by using a separate sensor. A process ofoperating the three-dimensional holographic display device according tothe disclosure is described below in detail with reference to FIG. 3 .

FIG. 3 is a view of an operation of a three-dimensional holographicdisplay device according to an embodiment.

Referring to FIG. 3 , an example of an LED array, for example, the LEDarray 110 of FIGS. 1 and 2 , including a plurality of light sources L₁to L₉ is illustrated. Although, for convenience of explanation, a casein which the number of light sources is nine is illustrated in FIG. 3 ,the number of light sources is not limited to the above example. Thenumber of light sources may be more or less than nine. In FIG. 3 , alight source shown as a black circle denotes a state in which light isoutput, and a light source shown as a white circle (or blank circle)denotes a state in which light is not output.

A plurality of light sources, for example, the light sources L₁ to L₉,included in an LED array may be controlled to sequentially output lightaccording to a preset pattern. For example, as illustrated in FIG. 3 ,after the light source L₁ outputs light, the light source L₂ may outputlight, and after the light source L₂ outputs light, the light source L₃may output light. After the light source L₉ outputs light in the samesequence, the light source L₁ may output light again. However, this ismerely an example, and the light sources L₁ to L₉ may be controlled tosequentially output light according to a different pattern. For example,the light sources L₁ to L₉ may output light in a reverse order of thepattern of FIG. 3 , or in an order of a certain or preset pattern.

A processor, for example, the processor 140 of FIGS. 1 and 2 , maygenerate a plurality of holographic signals each having depthinformation adjusted according to the arrangement location of each of aplurality of light sources, for example, the light sources L₁ to L₉, andcontrol an SLM, for example, the SLM 130 of FIGS. 1 and 2 , to modulatelight based on the holographic signal corresponding to a light sourcecurrently outputting light among the generated holographic signals. Inother words, the processor 140 may turn on and off the plurality oflight sources in a repeating sequence and may sequentially provide aplurality of signals to the SLM 130 such that each of the plurality ofsignals corresponds to a different step in the repeating sequence.

As the location of the light source that outputs light is changed, thelocation of the viewing window may be changed so that a viewpoint that auser views a holographic image may be changed. In other words, aholographic image may be formed at a plurality of viewing windows suchthat each of the plurality of viewing windows corresponds to a differentstep in the repeating sequence. Further, a location of each of theplurality of viewing windows may correspond to a location of a lightsource that is turned on during the corresponding step in the repeatingsequence. For example, as the light source that outputs light is changedfrom the light source L₁ to the light source L₂, the location of aviewing window may be changed from a viewing window VW₁ to a viewingwindow VW₂ as shown in FIG. 3 . As such, the location of a viewingwindow may be changed in a direction symmetrical to a direction in whichthe location of a light source is moved, with respect to a center of alens, for example, the lens 120 of FIGS. 1 and 2 , and the locationand/or angle of the pupil of the user to perceive a holographic imagemay be changed. Accordingly, for the user to correctly observe a desiredholographic image, the depth information of a holographic signal may beappropriately adjusted.

When a second light source outputs light after a first light sourceoutputs light according to a preset pattern, the processor may change aholographic image pattern displayed by the SLM at a timing when thesecond light source starts outputting light. A changed holographic imagepattern may be formed by a holographic signal (e.g., a secondholographic signal) having depth information (e.g., second depthinformation) adjusted according to the arrangement location of thesecond light source. In an example, when the light source L₂ outputslight after the light source L₁ outputs light, the processor may changethe holographic image pattern output by the SLM from Frame 1 to Frame 2.Frame 1 may have depth information adjusted considering the location ofthe viewing window VW₁ formed according to the location of the lightsource L₁ that outputs light, and Frame 2 may have depth informationadjusted considering the location of the viewing window VW₂ formedaccording to the location of the light source L₂ that outputs light.

When the light source L₂ starts outputting light directly after thelight source L₁ stops outputting light, a time when the light sourcestarts outputting light and a time when a displayed holographic imagepattern is changed by the SLM may be completely synchronized with eachother. However, the disclosure is not limited thereto, and when thelight source L₂ starts outputting light with a certain time intervalafter the light source L₁ stops outputting light, a time when the lightsource starts outputting light and a time when the holographic imagepattern is changed do not need to be completely synchronized with eachother, and the holographic image pattern may be changed before orsimultaneously when the light source starts outputting light.

As such, as a plurality of light sources, for example, the light sourcesL₁ to L₉, included in the LED array may be controlled to sequentiallyoutput light according to a preset pattern, for example, in an order ofL₁, L₂, . . . , L₉, and the SLM may modulate the light based on aholographic signal corresponding to a light source that outputs light ata specific time, the location of a viewing window, which enables theuser to normally perceive a holographic image, may be continuouslychanged.

When the LED array and the SLM are driven at a high enough speed, evenwhen the pupil of the user is located at any of a plurality of viewingwindows, for example, the viewing windows VW₁ to VW₉, respectivelycorresponding to a plurality of light sources, for example, the lightsources L₁ to L₉, at a specific time, the user may observe a holographicimage. In other words, according to the operating process of thethree-dimensional holographic display device of FIG. 3 , compared with acase of FIG. 2 in which a single light source, that is, the light source110 a, continuously outputs light, the size of an area where aholographic image is observed may be extended in proportion to thenumber of light sources. Accordingly, even when the location of thepupil of the user is moved within the extended area, the user maycontinuously observe a holographic image. When the number of lightsources is sufficiently large, the user may not substantially feelrestricted in movement.

To prevent the user from feeling a sense of difference according to themovement of a viewing window, the LED array and the SLM may be driven ata high enough speed. For example, the LED array may change, at least ata cycle of about 1 MHz, the light source that outputs light. Asillustrated in FIG. 3 , when the light source L₁ starts outputting lightat a point T₁, and the light source L₂ starts outputting light at apoint T₂, a cycle T of changing the light source that outputs light maybe T=T₂−T₁=(1 MHz)⁻¹=10⁻⁶ seconds. However, the disclosure is notlimited thereto, and the LED array may change the light source thatoutputs light, at a cycle of several hundreds to thousands of hertz ormore. The SLM may have a driving speed corresponding to the drivingspeed of the LED array.

Although FIG. 3 illustrates an example in which a plurality of viewingwindows respectively corresponding to a plurality of light sources donot overlap each other, the viewing windows may overlap each otheraccording to the size and brightness of each of the light sources, adistance between adjacent light sources, and the like. When the viewingwindows overlap each other, in some cases, a holographic imagecorresponding to one viewing window may appear to overlap a holographicimage corresponding to another viewing window. Furthermore, anafterimage of a holographic image may be seen due to the high speeddriving of the LED array and the SLM holographic image. In the followingdescription, various methods of observing a normal holographic image bya user are described in detail with reference to FIGS. 4 to 6 .

FIG. 4 is a view of a configuration of a three-dimensional holographicdisplay device according to an embodiment.

Referring to FIG. 4 , the three-dimensional holographic display device,for example, the three-dimensional holographic display device 10 of FIG.1 , may further include a filter 410 and an additional lens 420, inaddition to the LED array 110, the lens 120, and the SLM 130. As thesame description as the lens 120 is applied to the additional lens 420,a redundant description thereof is omitted.

The filter 410 may remove a noise component of light modulated by theSLM 130. As the filter 410 removes the noise component, an afterimage ofa holographic image generated due to the high speed driving of the LEDarray 110 and the SLM 130 may be removed. The filter 410 may dynamicallychange the filtering characteristics of removing a noise component. Inan example, the filter 410 may change filtering characteristics at ahigh enough speed to remove the afterimage of a holographic image causedby the high speed driving of the LED array 110 and the SLM 130.

FIG. 5 is a view of a process of implementing a multi-eye box by athree-dimensional holographic display device according to an embodiment.

In FIG. 5 , a light source shown as a black circle denotes a state inwhich light is output, and a light source shown as a white circledenotes a state in which light is not output. Furthermore, in FIG. 5 ,it is assumed that a distance between the LED array 110 and the lens 120is the same as a distance between the lens 120 and an observation area,and the size of the observation area is illustrated to be close to aratio of 1:1 in relation to the LED array 110. However, a person skilledin the art would easily understand that the size of an area of a viewingwindow may be changed according to the ratio between the distancebetween the LED array 110 and the lens 120 and the distance between thelens 120 and the observation area.

A processor, for example, the processor 140 of FIGS. 1 and 2 , may drivethe LED array 110 in units of light source sets, each light source setincluding at least two light sources. For example, as illustrated inFIG. 5 , the processor may drive the LED array 110 in units of sets ofnine light sources. In other words, the processor may control nine lightsources included in one light source set to simultaneously output light,and then nine light sources included in another light source set tosimultaneously output light.

The size of a unit viewing window (UVW) corresponding to one lightsource is limited by the pixel size of the SLM 130. However, when a setof nine light sources simultaneously outputs light, viewing windowsrespectively corresponding to the nine light sources may be overlappedwith each other. Accordingly, an intersection of sets of viewing windowsmay form an effective viewing window EVW in which noise is not present.A multi-eye box may be implemented in an area corresponding to theeffective viewing window EVW.

An eye box, which is an area that is actually taken by a holographicimage among the area in a viewing window, may mean an area includingimage information of the SLM 130. When the eye box is located at thepupil of the user, the user may observe a holographic image. Theprocessor may form the effective viewing window EVW by controlling alight source set including at least two light sources to simultaneouslyoutput light, and thus, a plurality of eye boxes may be formed in theeffective viewing window EVW. In other words, the user may observe aholographic image at various locations corresponding to the eye boxes inthe effective viewing window EVW.

Although FIG. 5 illustrates an example in which nine eye boxes areincluded in the effective viewing window EVW, the number of eye boxes inthe effective viewing window EVW may vary according to the size of aholographic image, the size and brightness of each of a plurality oflight sources, the distance between adjacent light sources, and thelike. The distance between at least two light sources included in alight source set may be set such that holographic images displayed inthe space by each of at least two light sources do not overlap eachother. However, the disclosure is not limited thereto.

According to the embodiment of FIG. 5 , as the processor drives the LEDarray 110 in units of light source sets, each light source set includingat least two light sources, as described with reference to FIG. 3 , highspeed scanning of viewing windows may be performed in units of effectiveviewing windows EVWs.

FIG. 6 is a view of a process of extending an eye box by athree-dimensional holographic display device according to an embodiment.

In FIG. 6 , a light source shown as a black circle denotes a state inwhich light is output, and a light source shown as a white circledenotes a state in which light is not output. Furthermore, in the bottomportion of FIG. 6 , a light source shown as a circle including a patterninside denotes a state in which light is output at a brightness lowerthan the light of the light source shown as a black circle. In FIG. 6 ,it is assumed that the distance between the LED array 110 and the lens120 is the same as the distance between the lens 120 and the observationarea, and the size of the observation area is illustrated to be close toa ratio of 1:1 in relation to the LED array 110. However, a personskilled in the art would easily understand that the size of an area of aviewing window may be changed according to the ratio between thedistance between the LED array 110 and the lens 120 and the distancebetween the lens 120 and the observation area.

A processor, for example, the processor 140 of FIGS. 1 and 2 , may drivethe LED array 110 in units of light source sets, each light source setincluding at least two light sources. Furthermore, the processor mayadjust the brightness of at least some of the at least two light sourcesincluded in a light source set to be different from the brightness ofthe other light sources. For example, as illustrated in FIG. 6 , theprocessor may control four light sources in addition to the nine lightsources that are controlled as shown in FIG. 5 to additionally outputlight. The brightness of the four light sources may be controlled to belower than that of the nine light sources.

When the size of a unit light source is too small, as the size of an eyebox formed at a viewing position decreases to be smaller than the sizeof the pupil of the user, it may be difficult for the user to normallyobserve a holographic image. In this case, the processor controlsadditional light sources, for example, the four light sources of amedium brightness in FIG. 6 , to simultaneously output light, so thatthe size of an eye box itself may be extended. For example, when thesize of an existing eye box (EYE BOX1) of FIG. 6 is smaller than that ofthe pupil of the user, as four light sources are additionallycontrolled, the size of a new eye box (EYE BOX2) may be increased to begreater than the size of the pupil of the user.

Furthermore, as the processor appropriately adjusts the brightness ofeach of a plurality of light sources, a holographic image may becalibrated. For example, as the processor maximizes the brightness of amain light source while appropriately adjusting the brightness of lightsources located around the main light source, a holographic image ofhigh resolution may be provided to the user. Furthermore, when it isdetermined that at least two light sources included in a light sourceset include a defective light source, the processor may adjust thebrightness of light sources around the defective light source tocompensate for the defect.

FIG. 7 is a view of a configuration of an LED array according to anembodiment.

Referring to FIG. 7 , the LED array 110 may include a first area 710corresponding to light sources for displaying a holographic image (e.g.,a first holographic image) perceived by a left eye of the user and asecond area 720 corresponding to light sources for displaying aholographic image (e.g., a second holographic image) perceived by aright eye of the user. Each of the first area 710 and the second area720 may be driven based on various operating methods of theabove-described 3D holographic display device.

When the distance between the LED array 110 and a lens, for example, thelens 120 of FIG. 1 , is the same as the distance between the lens and aviewing position of the user, a distance ES between the first area 710and the second area 720 may be about 65 mm, which is an averagebinocular spacing of a user. However, the disclosure is not limitedthereto, and the distance ES between the first area 710 and the secondarea 720 may be appropriately set according to the focal length of alens and the like. A processor, for example, the processor 140 of FIGS.1 and 2 , may assign at least some of the light sources included in theLED array 110 to the first area 710, and the other light sources to thesecond area 720, and thus, the distance ES between the first area 710and the second area 720 may be easily adjusted.

Referring back to FIG. 1 , the three-dimensional holographic displaydevice 10 may further include a driving device 150 that moves the LEDarray 110 in at least one of a first direction, a second directionperpendicular to the first direction, and a third directionperpendicular to both of the first direction and the second direction,or rotates the LED array 110 around at least one of the first direction,the second direction, and the third direction, as an axis. For example,in the viewpoint of facing the LED array 110 from the front side, thedriving device 150 may move the LED array 110 in at least one of avertical direction, a horizontal direction, and a depth direction, orrotate the LED array 110 around at least one of the vertical direction,the horizontal direction, and the depth direction, as an axis.

As described above with reference to FIG. 3 , even when the observationarea is extended through the high speed driving of the LED array 110 andthe SLM 130, when the user is located outside the extended observationarea, the three-dimensional holographic display device 10 may change thelocation of the LED array 110 by using the driving device 150.Accordingly, the observation area may be additionally extended. Forexample, fine tuning of the observation area may be achieved by thecontrol of the light sources included in the LED array 110, and tuningin a large scale may be achieved by the control of the driving device150. Furthermore, when the LED array 110 includes a defective lightsource, the driving device 150 may replace the defective light sourcewith another light source by moving the LED array 110.

FIG. 8 is a flowchart of a method of operating a three-dimensionalholographic display device, according to an embodiment.

Referring to FIG. 8 , the method of operating a three-dimensionalholographic display device may include operations that are processed ina time series in the three-dimensional holographic display device 10 ofFIG. 1 . Accordingly, it may be seen that the above descriptions givenwith reference to FIGS. 1 to 7 , although omitted below, may be appliedto the method of operating a three-dimensional holographic displaydevice of FIG. 8 .

In operation 810, the three-dimensional holographic display device maygenerate holographic signals having depth information adjusted accordingto the arrangement location of each of a plurality of light sourcesincluded in an LED array. A holographic signal may include a CGH.

In operation 820, the three-dimensional holographic display device maycontrol the light sources to sequentially output light according to apreset pattern. In an example, the three-dimensional holographic displaydevice may change a light source that outputs light at a cycle of atleast 1 MHz. However, the disclosure is not limited thereto.

In operation 830, the three-dimensional holographic display device maycontrol an SLM to modulate light based on a holographic signalcorresponding to a light source that currently outputs light among thegenerated holographic signals. As the location of the light source thatoutputs light is changed, the location of a viewing window may bechanged, and a viewpoint in which a holographic image is visible may bechanged. Accordingly, depth information of a holographic signal isappropriately adjusted for a user to appropriately observe an intendedholographic image.

Accordingly, when a second light source outputs light after a firstlight source outputs light according to a preset pattern, thethree-dimensional holographic display device may change a holographicimage pattern displayed by the SLM, at a timing when the second lightsource starts outputting light. The changed holographic image patternmay be formed by a holographic signal having depth information adjustedaccording to the arrangement location of the second light source.

The operations of FIG. 8 may not necessarily be performed in thedescribed order. For example, operation 810 may be previously performedbefore operation 820 and operation 830 are performed, and may besubstantially and simultaneously performed with operation 820 andoperation 830. Although operation 820 and operation 830 correspond tooperations that are performed together, specific start timings of therespective operations may not be completely matched. Furthermore,operation 810 may be performed only once at the beginning, and operation820 and operation 830 only may be repeated. However, the disclosure isnot limited thereto, and all operations may be repeatedly performed.

The three-dimensional holographic display device may remove a noisecomponent of light modulated by the SLM. For example, as thethree-dimensional holographic display device additionally includes anoise filter at the rear of the SLM, the noise component of the lightmodulated by the SLM may be removed.

The three-dimensional holographic display device may drive an LED arrayin units of light source sets, each light source set including at leasttwo light sources. In an example, the distance between at least twolight sources included in a light source set may be set such thatholographic images displayed in a space respectively by at least twolight sources do not overlap each other. However, the disclosure is notlimited thereto.

In an example, the three-dimensional holographic display device mayadjust the brightness of at least some of at least two light sourcesincluded in a light source set to be different from the brightness ofother light sources. When the size of a unit light source is too small,the size of an eye box formed at a viewing position decreases to besmaller than the size of a pupil of a user, and thus it may be difficultfor the user to normally observe a holographic image. In this case, asthe three-dimensional holographic display device maximizes thebrightness of a main light source while appropriately adjusting thebrightness of light sources located around the main light source, thesize of an eye box may be extended.

Furthermore, when it is determined that at least two light sourcesincluded in a light source set include a defective light source, thethree-dimensional holographic display device may adjust the brightnessof light sources around the defective light source to compensate for thedefect.

According to an embodiment, the three-dimensional holographic displaydevice may move an LED array in at least one of a first direction, asecond direction perpendicular to the first direction, and a thirddirection perpendicular to both of the first direction and the seconddirection, or rotate the LED array around at least one of the firstdirection, the second direction, and the third direction, as an axis

The above-described method of operating a three-dimensional holographicdisplay device may be recorded on a computer-readable recording mediumhaving recorded thereon one or more programs including instructions forexecuting the method. Examples of the computer-readable recording mediuminclude magnetic media, e.g., hard disks, floppy disks, and magnetictapes, optical media, e.g., compact disc read only memories (CD-ROMs)and digital versatile disks (DVDs), magneto-optical media, e.g.,floptical disks, and hardware devices configured to store and executeprogram commands, for example, programming modules, e.g., read onlymemories (ROMs), random access memories (RAMs), flash memories. Also,the program command may include not only machine code created by acompiler but also high-level programming language executable by acomputer using an interpreter.

The description of the following embodiments should not be construed aslimiting the scope of rights, and contents that can be easily inferredby those skilled in the art should be construed as belonging to thescope of the present specification.

It should be understood that embodiments described herein should beconsidered in a descriptive sense only and not for purposes oflimitation. Descriptions of features or aspects within each embodimentshould typically be considered as available for other similar featuresor aspects in other embodiments. While one or more embodiments have beendescribed with reference to the figures, it will be understood by thoseof ordinary skill in the art that various changes in form and detailsmay be made therein without departing from the spirit and scope asdefined by the following claims and their equivalents.

What is claimed is:
 1. A three-dimensional holographic display devicecomprising: a light emitting diode (LED) array comprising a plurality oflight sources, wherein the plurality of light sources comprise aplurality of light source sets, each of the plurality of light sourcesets comprising at least two light sources among the plurality of lightsources; a lens configured to refract light incident from the LED array;a spatial light modulator (SLM) configured to modulate light incidentfrom the lens; and a processor configured to: control the plurality oflight source sets in a unit of light source set to sequentially outputlight according to a preset repeating pattern; generate a plurality ofholographic signals each comprising depth information adjusted accordingto an arrangement location of each of the plurality of light source setsin the LED array; and for each of the plurality of light source sets,control the SLM to modulate the light based on a holographic signalcorresponding to a light source set of the plurality of light sourcesets, wherein the LED array changes a light source set that outputslight at a cycle of at least 1 MHz.
 2. The three-dimensional holographicdisplay device of claim 1, wherein, when a second light source set ofthe plurality of light source sets outputs light after a first lightsource set of the plurality of light source sets outputs light accordingto the preset repeating pattern, the processor changes a holographicimage pattern formed by a first holographic signal of the plurality ofholographic signals and displayed by the SLM at a timing when the secondlight source set starts outputting the light, and wherein the changedholographic image pattern is formed by a second holographic signal ofthe plurality of holographic signals, the second holographic signalcomprising depth information adjusted according to an arrangementlocation of the second light source set in the LED array.
 3. Thethree-dimensional holographic display device of claim 1, furthercomprising a filter configured to remove a noise component of the lightmodulated by the SLM.
 4. The three-dimensional holographic displaydevice of claim 1, wherein for each of the plurality of light sourcesets, a distance between the at least two light sources in the lightsource set is set such that holographic images displayed in a spacerespectively by the at least two light sources do not overlap eachother.
 5. The three-dimensional holographic display device of claim 1,wherein for each of the plurality of light source sets, the processor isfurther configured to adjust a brightness of at least some light sourcesamong the at least two light sources in the light source set to bedifferent from a brightness of other light sources in the light sourceset.
 6. The three-dimensional holographic display device of claim 1,wherein the processor is further configured to, when it is determinedthat the at least two light sources in a light source set of theplurality of light source sets comprise a defective light source, adjusta brightness of light sources around the defective light source tocompensate for a defect.
 7. The three-dimensional holographic displaydevice of claim 1, wherein the LED array comprises a first areacomprising light sources of the plurality of light sources fordisplaying a first holographic image perceived by a left eye of a userand a second area comprising light sources of the plurality of lightsources for displaying a second holographic image perceived by a righteye of the user.
 8. The three-dimensional holographic display device ofclaim 1, further comprising a driving device configured to move the LEDarray in at least one of a first direction, a second directionperpendicular to the first direction, and a third directionperpendicular to both of the first direction and the second direction,or rotate the LED array around at least one of the first direction, thesecond direction, and the third direction, as an axis.
 9. A method ofoperating a three-dimensional holographic display device, the methodcomprising: generating a plurality of holographic signals eachcomprising depth information adjusted according to an arrangementlocation of each of a plurality of light source sets in a light emittingdiode (LED) array, wherein the LED array comprises a plurality of lightsources and the plurality of light sources comprise the plurality oflight source sets, each of the plurality of light source sets comprisingat least two light sources among the plurality of light sources;controlling all of the plurality of light source sets in a unit of lightsource set to sequentially output light according to a preset repeatingpattern; and for each of the plurality of light source sets, controllinga spatial light modulator (SLM) to modulate light incident from the LEDarray based on a holographic signal corresponding to a light source setof the plurality of light source sets, wherein the controlling of theplurality of light source sets comprises changing a light source setthat outputs light at a cycle of at least 1 MHz.
 10. The method of claim9, further comprising, when a second light source set of the pluralityof light source sets outputs light after a first light source set of theplurality of light sets outputs light according to the preset pattern,changing a holographic image pattern formed by a first holographicsignal of the plurality of holographic signals and displayed by the SLMat a timing when the second light source set starts outputting thelight, wherein the changed holographic image pattern is formed by asecond holographic signal of the plurality of holographic signals, thesecond holographic signal comprising depth information adjustedaccording to an arrangement location of the second light source set inthe LED array.
 11. The method of claim 9, further comprising removing,by a filter of the three-dimensional holographic display device, a noisecomponent of the light modulated by the SLM.
 12. The method of claim 9,wherein for each of the plurality of light source sets, a distancebetween the at least two light sources in the light source set is setsuch that holographic images displayed in a space respectively by the atleast two light sources do not overlap each other.
 13. The method ofclaim 9, further comprising, for each of the plurality of light sourcesets, adjusting a brightness of at least some light sources among the atleast two light sources in the light source set to be different from abrightness of other light sources in the light source set.
 14. Themethod of claim 9, further comprising, when it is determined that the atleast two light sources in a light source set of the plurality of lightsource sets comprise a defective light source, adjusting a brightness oflight sources around the defective light source to compensate for adefect.
 15. The method of claim 9, further comprising moving the LEDarray in at least one of a first direction, a second directionperpendicular to the first direction, and a third directionperpendicular to both of the first direction and the second direction,or rotating the LED array around at least one of the first direction,the second direction, and the third direction, as an axis.
 16. Anon-transitory computer-readable recording medium having recordedthereon a program for executing the method of claim
 9. 17. A holographicdisplay device comprising: a plurality of light sources comprising aplurality of light source sets configured to be operated independentlyof each other, wherein each of the plurality of light source setscomprising at least two light sources among the plurality of lightsources; a spatial light modulator (SLM) that receives light emitted bythe plurality of light source sets; and a processor configured to: turnon and off all of the plurality of light source sets in a unit of lightsource set in a preset repeating sequence; and sequentially provide aplurality of signals to the SLM, each of the plurality of signalscorresponding to a different step in the repeating sequence and havingdepth information adjusted according to an arrangement location of eachof the plurality of light source sets in the plurality of light sources,wherein the plurality of light source sets changes a light source setthat outputs light, at a cycle of at least 1 MHz.
 18. The holographicdisplay device of claim 17, wherein the holographic display device isconfigured to form a holographic image at a plurality of viewingwindows, each of the plurality of viewing windows corresponding to adifferent step in the repeating sequence.
 19. The holographic displaydevice of claim 18, wherein a location of each of the plurality ofviewing windows corresponds to a location of one or more light sources,of the plurality of light sources, that is turned on during thecorresponding step in the repeating sequence.
 20. The holographicdisplay device of claim 17, wherein when a second light source set ofthe plurality of light source sets outputs light after a first lightsource set of the plurality of light source sets outputs light accordingto the preset repeating sequence, the processor changes a holographicimage pattern formed by a first signal of the plurality of signals anddisplayed by the SLM at a timing when the second light source set startsoutputting the light, and wherein the changed holographic image patternis formed by a second signal of the plurality of signals, the secondsignal comprising depth information adjusted according to an arrangementlocation of the second light source set in the plurality of lightsources.